1. Field of the Invention
The present invention relates to an electron emitting device, a method for producing the same, and a display apparatus and an electron beam drawing apparatus utilizing said electron emitting device.
2. Related Background Art
Conventionally used electron emitting devices are mostly those utilizing a hot cathode, but the electron emission by the hot cathode has been associated with drawbacks such as a large energy loss by heating and the necessity for preliminary heating.
For resolving these drawbacks there have been proposed various electron emitting devices of cold cathode type, including a field effect type electron emitting device in which a high electric field is locally generated and the electron emission is realized by field emission.
FIG. 1 is a schematic partial cross-sectional view showing an example of such field effect electron emitting device, and FIGS. 2A to 2D are schematic views showing the steps for producing said device.
As shown in FIG. 1, said field effect electron emitting device is composed of a substrate 101 composed for example of Si; a point-shaped electron emitting part 108 composed for example of molybdenum (Mo) and formed on said substrate; an insulating layer 102 composed for example of SiO.sub.2 and having an aperture around said point-shaped electron emitting part 108; and an electrode 109 the end of which is positioned close to the pointed part of the conical shape.
In such electron emitting device, electrons are emitted from the pointed part where the intensity of electric field is strong, when a voltage is applied between the substrate 101 and the electrode 109.
Such field effect electron emitting device utilizing microfabrication technology is for example reported by C. A. Spindt et al. in Journal of Applied Physics, Vol. 47, No. 12, 1976, p. 5246. Said electron emitting device is obtained by forming a hole of a diameter of about 1.5 .mu.m in a thin film of SiO.sub.2 and a gate electrode formed in succession on a Si substrate, and further forming, by metal deposition, a conical emitter electrode with a diameter of the pointed end not exceeding 1000.ANG. for field emission.
The above-mentioned electron emitting device is generally prepared by the following process;
(1) First, as shown in FIG. 2A, an insulating layer 102 for example of a SiO.sub.2 film of a thickness of 1-1.2 .mu.m is formed on the substrate 101 composed for example of Si. PA1 (2) Then, on said insulating layer 102, a Mo layer 109 of a thickness for example of about 0.4 .mu.m is formed for example by electron beam evaporation. PA1 (3) An electron beam resist, composed for example of PMMA (polymethylmethacrylate) is applied by spin coating on said Mo layer 109. PA1 (4) Said electron beam resist is irradiated with an electron beam in a desired pattern, and is then partially removed for example with isopropyl alcohol according to said desired pattern. PA1 (5) The Mo layer 109 is selectively etched according to the resist pattern, to form a first aperture 103. PA1 (6) Then the remaining electron beam resist is completely removed, and the insulating layer 102 is etched with hydrofluoric acid to form a second aperture 704 (FIG. 2A). PA1 (7) Then the substrate 101 is rotated about an axis X with an inclination by a predetermined angle .theta., and aluminum is deposited by evaporation onto the Mo layer 109, thereby forming an Al layer 105. Since aluminum is deposited also on the lateral face of the Mo layer 109, the diameter of the first aperture 103 can be arbitrarily reduced by the control of amount of evaporation (FIG. 2B). PA1 irradiating the surface of a substrate of an insulating material with a focused ion beam along an arbitrary circle defined on said surface, thereby forming an ion implanted area in said substrate; PA1 chemically etching said substrate to eliminate said ion implanted area thereby forming an electric field forming space having a projection at the bottom thereof; PA1 covering said projection with a conductive material to form a point-shaped electron-emitting part; and PA1 covering the surface of said substrate, excluding said electric field forming space, with a conductive material thereby forming an electrode for forming an electric field in cooperation with said point-shaped electron emitting part. PA1 irradiating the surface of a substrate composed of a semiconductive or conductive material having a surfacial insulating layer with a focused ion beam along an arbitrary circle defined on said surface, thereby forming an ion implanted area in said substrate; PA1 chemically etching said substrate to eliminate said ion implanted area thereby forming an electric field forming space having a projection at the bottom thereof; PA1 covering said projection with a conductive material to form a point-shaped electron emitting part; and PA1 covering the surface of said substrate, excluding said electric field forming space, with a conductive material thereby forming an electrode for forming an electric field in cooperation with said point-shaped electron emitting part. PA1 irradiating the surface of a substrate composed of an insulating material with a focused ion beam along an arbitrary race track-shaped trajectory defined on said surface, thereby forming an ion implanted area in said substrate; PA1 chemically etching said substrate to eliminate said ion implanted area thereby forming an electric field forming space having a line-shaped projection at the bottom thereof; PA1 covering said line-shaped projection with a conductive material to form a line-shaped electron emitting part; and PA1 covering the surface of said substrate, excluding said electric field forming space, with a conductive material thereby forming an electrode for forming an electric field in cooperation with said line-shaped electron emitting part. PA1 irradiating the surface of a substrate composed of a semiconductive or conductive material having a surfacial insulating layer with a focused ion beam along an arbitrary race track-shaped trajectory defined on said surface, thereby forming an ion implanted area in said substrate; PA1 chemically etching said substrate to eliminate said ion implanted area thereby forming an electric field forming space having a line-shaped projection at the bottom thereof; PA1 covering said line-shaped projection with a conductive material to form a line-shaped electron emitting part; and PA1 covering the surface of said substrate, excluding said electric field forming space, with a conductive material thereby forming an electrode for forming an electric field in cooperation with said line-shaped electron emitting part. PA1 irradiating a substrate with an ion beam in a desired pattern; PA1 etching said substrate irradiated with said ion beam for eliminating at least the part irradiated by said ion beam; and PA1 depositing a conductive material on said etched substrate. PA1 irradiating the surface of a substrate of an insulating material with a focused ion beam along an arbitrary circle defined on said surface, thereby forming an ion implanted area in said substrate; PA1 chemically etching said substrate to eliminate said ion implanted area thereby forming an electric field forming space having a projection at the bottom thereof; PA1 covering said projection with a conductive material to form a point-shaped electron emitting part; and PA1 covering the surface of said substrate, excluding said electric field forming space, with a conductive material thereby forming an electrode for forming an electric field in cooperation with said point-shaped electron emitting part. PA1 irradiating the surface of a substrate composed of an insulating material with a focused ion beam along an arbitrary race track-shaped trajectory defined on said surface, thereby forming an ion implanted area in said substrate; PA1 chemically etching said substrate to eliminate said ion implanted area thereby forming an electric field forming space having a line-shaped projection at the bottom thereof; PA1 covering said line-shaped projection with a conductive material to form a line-shaped electron emitting part; and PA1 covering the surface of said substrate, excluding said electric field forming space, with a conductive material thereby forming an electrode for forming an electric field in cooperation with said line-shaped electron emitting part.
Subsequently Mo is deposited for example by electron beam evaporation perpendicularly to the substrate 101. Since Mo is deposited not only on the Al layer 105 and the substrate 101 but also on the lateral face of the Al layer 105, the diameter of the first aperture 103 decreases gradually with the deposition of a Mo layer 106. As the area of deposition of Mo on the Si substrate decreases according to the decrease in the diameter of said first aperture 103, there is a substantially formed conical electrode 108 on the substrate 101 (FIG. 2C).
Finally the field effect electron emitting device is obtained by removing the Mo layer 106 and the Al layer 105, as shown in FIG. 8D.
It is however difficult, in the above-explained process, to prepare a smaller field effect electron emitting device, for example the device smaller than 3 .mu.m, with a high production yield, since the formation of the field forming space and the electron emitting part involves complicated technology such as oblique evaporation.
Also in the above-explained process for producing the electron emitting device, since the formation of the conical emitter electrode 108 is achieved by metal deposition, utilizing the shape of the aperture 103 in the Al layer 109, the reproducibility of the shape (height, angle, bottom diameter etc.) of said emitter electrode 108 is low, resulting in poor production yield and unsatisfactory uniformity of the shape or performance of the device. The production yield is particularly poor when plural electron emitting devices are formed at the same time on a Si substrate, resulting in a high cost. Since this tendency becomes more marked as the size of the electron emitting device becomes smaller, it has been difficult to obtain finer electron emitting devices.
Further, the manufacturing process of the above-explained conventional electron emitting device is very complex, resulting in the high cost of the device.